1. Field of the Invention
The present invention relates to a motion assist apparatus adapted to assist a motion of an upper body to return to a basic posture from a tilted state and a motion of maintaining a tilted posture.
2. Description of the Related Art
There has conventionally been known a motion assist apparatus provided with thigh abutting members to be attached to the legs of a user, a chest abutting member to be attached to the upper body of the user, thigh support arms connected to the thigh abutting members, upper body support anus connected to the chest abutting member, and a waist abutting member to be attached to the waist of the user (refer to Japanese Patent No. 2736619 (hereinafter referred to as Patent Document 1)).
In the motion assist apparatus, a force from the elastic force of a coil spring used for connecting the thigh support arms and the waist abutting member and the elastic force of the upper body support arms themselves increases as the upper body relatively tilts with respect to legs, and the force acts to the user to increase the angle formed by the thigh support arms and the upper body support arms. This force is applied to a user to assist his or her motion to set the tilted upper body back to a basic posture (the posture in which the relative positions of the upper body and the legs have been set back to the positions at which the user is in a normal upright state).
Further, in the motion assist apparatus, the upper body support arms are vertically slidably installed with respect to the waist abutting member, and the position at which a chest abutting member connected to the upper body support arms is abutted against the user is adjustable in a vertical direction within a predetermined range.
According to the motion assist apparatus described in Patent Document 1, the force for restraining, the tilt of the upper body relative to the legs is applied to the user by the predesigned elastic forces of the constituent members. Hence, there has been a possibility that the motion assist apparatus could cause a user to feel uncomfortable when the force for assisting his or her motion is applied to the user, depending on the body shape of the user.